build.sh: move doc build before proto & libs
build.sh: move doc build before proto & libs

Now that many protocol & library modules include DocBook documentation
that uses the stylesheets from xorg-sgml-doctools to build, install
those first.

Signed-off-by: Alan Coopersmith <ea3248f8c2440b9439894eab21ef26209b22bacf@oracle.com>
Reviewed-by: Gaetan Nadon <8a8cc541338200f67d4d0bcb65c78b6166649462@videotron.ca>

freedesktop-unofficial-mirror/xorg__util__modular,freedesktop-unofficial-mirror/xorg__util__modular,freedesktop-unofficial-mirror/xorg__util__modular